2) A car is intially, at t = 0 s, moving at 10 m/s in the positive x direction w

Question

2) A car is intially, at t = 0 s, moving at 10 m/s in the positive x direction while accelerating constantly and after 5 seconds it has traveled a displacement of 100 meters in the positive x direction. It then, instantaneously (not physically realistic, however), changes its acceleration (second accelearation is constant) and 10 seconds after it has changed its acceleration, its displacement is 50 meters in the negative x direction of where it intially started (50 meters in the negative x direction of where it was at t = 0 s).

Answer the following:

a) What is the velocity of the car when it is 50 meters in the negative x direction of where it initially started?

b) What is the average velocity for the whole trip?

c) What is the average speed of the whole trip remembering average speed is the total distance traveled divided by the time taken to travel that distance?

d) Starting at t = 0 s, how long does it take (in total) for the car’s average velocity to be zero?

I need the most help with understanding C and D. My professor says that the average speed is somehow 350m/15sec and I am comfused to how it is 350m and not 250m.

Explanation / Answer

c)

Total displacement = T=0 to t= 5

1st Acceleration is a

= 100 = 10t + 1/2 at^2

a = (100-50)*2/(25) = 4 /s

Speed after 5 second = u+at = 10+4*5 = 30 m/s

Distance traveled in t=5 to 10 = 30 *5 + 0.5* 4*25 = 200 m

Distance traveled in last 5 second = 50

Total distance = 100+200+50 = 350 m

Avg speed = 350/15

d)

Avg velocity = Avg displacement / time =0

means avg displacement = 0

at t= 12 second displacement will be zero

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.